A wind turbine is provided with a rotor which comprises a number of blades, normally three, and a hub on which the blades are mounted. The blades are large, about 20 m to 50 m long, and their tip can reach a speed of 250 km/h.
Inside the blade, water is accumulated due to condensation. This accumulation of water in the interior of the blade is harmful in two respects: a sizeable amount of water will act as a displaceable ballast and will impair the normal functioning of the blade; and, when the blade is upright and idling, i.e., out of operation, the water will flow down the blade and may enter the hub, which houses some electric ware that can be damaged if it comes in contact with water.
Furthermore, the blades are hollow and during its manufacture, some dirt can remain inside them. Upon the rotation of the blade, this dirt eventually becomes dust and mixes with the condensation water to form some dough that is centrifuged to the tip of the blade.
It is known in the art to drill a drain bore in the tip of the blade to define a passage through which water is intended to drain off. However, when the blades rotate at high speed, any singularity or unevenness on the tip surface can produce an intense noise. Thus, this bore must be small, not more than 6 millimeters (mm) wide, in order to prevent the bore from making a big noise upon rotation. Unfortunately, the mixture of dust and water propelled to the tip by the centrifugal force is likely to obstruct such a narrow passage.